<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <meta http-equiv="X-UA-Compatible" content="ie=edge">
   <title>Document</title>
   <style>
      div{
         width: 400px;
         height: 400px;
         border:1px solid #000000;
         background: url(../2day/imgaes/dog.jpg) no-repeat;
          /* 图片的宽高设置 */
         /* background-size: 400px 400px; */
         /* 一个值为宽度，背景图片会的比例缩放 */
         /* background-size: 400px; */
         box-sizing: border-box;
      }
   </style>
</head>
<body>
   <div class="box">

   </div>
</body>
</html>